Sanding before heat treat?

A

Alfazulu

Joined
Mar 24, 2016
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Hey guys, what do y'all think about sanding before heat treat? It occurred to me that before I send this batch of 9 knives I just ground to heat treat, maybe I should go ahead and sand out some of the deep scratches. Do any of you do this, or do you do ALL of the sanding/finishing after heat treat? I understand if you go back to the grinder after heat treat that it's pointless (except on the flats), but I don't think I'll have to do much, if anything, on the grinder when I get them back. I'm planning to just soak them in vinegar, then go to the sandpaper. Is there a problem with doing it this way? The only issue I see is that you can only grind so thin before heat treat, and if you want to go thinner, it must be done after heat treat. However, I'm ok with the 0.020" that these are at pre heat.

I've only made one finished knife so far (CPM 10V at 64Hrc) and remember it being next to impossible to sand out the deeper scratches after heat treat. I know that's a particularly tough steel to work on, but I'd imagine this batch (CPM 20CV @ 61-62Hrc) will also be pretty tough. Anyway, I sanded them all to 120grit, removing all the deep scratches. I'm HOPING I can pick right back up with 120grit, or maybe 180grit when they come back from heat treat. What do you all do? Am I really saving some time/handache?
 
Try it both ways, see which is better for you. If I am doing a knife with thinner stock I would profile, drill then send. Thicker stock, 60 the 120 at least then heat treat.

hope this helps
 
If you're using high wear resistance particle metal steels I would STRONGLY suggest bringing your knives to the closest of final dimensions pre-heat treat, hand finishing to whatever your final finish will be, THEN heat treating. With most of the higher alloys I use, it's almost impossible to finish afterward. You really want to just have to remove the oxides from heat treat.

This is probably a question that should be in the Knifemaker forums, so consider asking the mods to move it for you. Probably get more answers there...
 
Heck, I get as close as possible to finished before HT, regardless of the steel. Of course, it's much more important on stainless than carbon.
 
Jwgriesser said:
Do you consider ABE-Lmthis type of steel Matt?
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Not at all. AEB-L has no wear resistance, really. I profile my chef knives out, heat treat them, and grind them hardened. Good ceramic belts grind it very easily.
 
With most blades, I take it to a really clean 400 grit finish pre-HT. For thin blades, I either do all the grinding post-HT or just rough in the bevels partway with 220 grit.
 
Your first knife was 10V @ 64rc - excuse me sir your giant brass balls are showing.
I would finish the blade to a complete finish befor heat treating.
 
Amen, take it to 400 or 600 before hear treat. If you get them nice now, it really reduces the work afterwards, and makes a nice job.

Sent from my SAMSUNG-SM-G800A using Tapatalk
 
Let's see this knife and the batch of knives your sending out
 
I'm just leaving an opinion here.. but with the high wear resistance alloys, CPM s35Vn, S90v(a real PITA!), Elmax, M390. etc, etc etc.. Nobody is taking in consideration how is gonna come out from HT, If you grind the bevels to 0, from ricaso to the tip, you dont guarantee that the blade is going to come out straight!

At least that's my experience with N695, 14c28n, D2, CPM S90V, ATS-34... if it's thin stock i rather grind pots HT, if it's S90V i remove as much material as i can but leaving on the total of the blade full thickness, then i grind the bevels to final shape
 
Just my opinion, buy why take a carbon steel much beyond 120 grit pre heat treat? The edge needs to be at least .020" thick, often thicker for peace of mind, to handle the quench. Most of my knives have a pre sharpened edge of .010" or less, so there is no reason to go above 120 grit, you're removing a bit of steel anyway. Now stainless is a different story altogether, because the quench is often air or plates, and the edge can be taken to basically final dimensions. In that case, there really is no post heat treat grinding to do, so take the pre heat treat finish to as fine of a grit as you want it.
 
samuraistuart said:
Just my opinion, buy why take a carbon steel much beyond 120 grit pre heat treat? The edge needs to be at least .020" thick, often thicker for peace of mind, to handle the quench. Most of my knives have a pre sharpened edge of .010" or less, so there is no reason to go above 120 grit, you're removing a bit of steel anyway. Now stainless is a different story altogether, because the quench is often air or plates, and the edge can be taken to basically final dimensions. In that case, there really is no post heat treat grinding to do, so take the pre heat treat finish to as fine of a grit as you want it.
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What about decarburization on the surface ?
 
samuraistuart said:
Just my opinion, buy why take a carbon steel much beyond 120 grit pre heat treat? The edge needs to be at least .020" thick, often thicker for peace of mind, to handle the quench. Most of my knives have a pre sharpened edge of .010" or less, so there is no reason to go above 120 grit, you're removing a bit of steel anyway. Now stainless is a different story altogether, because the quench is often air or plates, and the edge can be taken to basically final dimensions. In that case, there really is no post heat treat grinding to do, so take the pre heat treat finish to as fine of a grit as you want it.
Click to expand...

i guess you forgot the joys of sanding hardened 1.2519
scott
 
Natlek, I use ATP 641, so decarb is a non issue, whether it's carbon or stainless. (Peter's does my SS, they use ATP or something similar)

Scott, not sure what you mean. Again, the edge needs to be at least .020" pre quench, and sub .010" pre sharpening. So why bother going above 120 grit, if you're gonna "erase" it anyway with a post heat treat grind? Yeah, it's a pain to hand sand, but it has to be done. It's not like I can take 1.2519, or any oil hardening steel, to final edge dimensions pre heat treat. I wish. Do you take 1.2519 to final dimensions before hardening?
 
When I use CPM 154 I hand sand to 400 grit and the edge is as thin as I will make it. I send my blades to Paul Bos heat treating. They come back perfect. there is no scale on the blades. I then start with 400 grit and go up to 1200. I used to send them off after 220 on the grinder. It took a long, long time to get the 220 scratches out.
When I use a steel like W-2, I will go back to the grinder after heat treat, so hand sanding to 400 grit is a waste of time.
 
I agree with Tom Lewis. When grinding stainless steel I finish the blade to almost done except I leave 25 or 30 thousands on the edge to avoid a warp. I also use Paul Bos heat treat and the blades come back looking great and I need only to take the edge down to final geometry and use a very fine belt slow to finish. I can do a high polish from there easily ( of course hand sanding to at least 2000 grit ) or use a 400 grit cork belt and finish with a ultrafine scotchbrite belt. Larry P.S. The photos are two different knives. LL

xVnP4lcm.jpg


5ZSKajom.jpg
 
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JTknives said:
Your first knife was 10V @ 64rc - excuse me sir your giant brass balls are showing.
I would finish the blade to a complete finish befor heat treating.
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Hahaha! It wasn't too bad to work with. Of course, it was my first, so I didn't have any perspective on easy vs hard. AFTER heat treat, however, it was impossible to finish. That's why it looks rough. I went with CPM 10V as a first knife because I had been wanting to try both 10V and making a knife. I figured it would be the cheapest way to get a 10V knife.
IMG_9297.jpg


JTknives said:
Let's see this knife and the batch of knives your sending out
Click to expand...

IMG_0282.jpg


You can go to this thread to see more pics of them:

http://www.bladeforums.com/forums/s...ew-new-knives-in-the-works-for-new-knifemaker

JPuri said:
I'm just leaving an opinion here.. but with the high wear resistance alloys, CPM s35Vn, S90v(a real PITA!), Elmax, M390. etc, etc etc.. Nobody is taking in consideration how is gonna come out from HT, If you grind the bevels to 0, from ricaso to the tip, you dont guarantee that the blade is going to come out straight!

At least that's my experience with N695, 14c28n, D2, CPM S90V, ATS-34... if it's thin stock i rather grind pots HT, if it's S90V i remove as much material as i can but leaving on the total of the blade full thickness, then i grind the bevels to final shape
Click to expand...

I'm not grinding them to zero edge. I'm leaving them at about 0.015-0.020", per Brad at Peter's Heat Treat. He said that should keep them straight during the quench. I know that's not a super thin edge, but it's good enough for me. I'm not making these for knife nuts. That behind-the-edge thickness will be durable and still perform well. I can always grind them thinner after if I want, but I likely won't.

Thanks for all the replies, guys. You have confirmed what I suspected. I'm going to take them up to a finer grit before sending them out. I will likely go to 220 or 320 grit. Maybe 400. We will see.
 
I think the thing about grinding bevels pre or post HT is how thick the material is. For blades less than .092", especially down around .070" and less, I really prefer profile, drill holes, HT, then grind bevels. If blade material is >.1" or (1/8"?) I prefer to profile, bevel to .010" edge or so, drill holes, HT, then finish.
 
Alfazulu said:
Hahaha! It wasn't too bad to work with. Of course, it was my first, so I didn't have any perspective on easy vs hard. AFTER heat treat, however, it was impossible to finish. That's why it looks rough. I went with CPM 10V as a first knife because I had been wanting to try both 10V and making a knife. I figured it would be the cheapest way to get a 10V knife.
IMG_9297.jpg




IMG_0282.jpg


You can go to this thread to see more pics of them:

http://www.bladeforums.com/forums/s...ew-new-knives-in-the-works-for-new-knifemaker



I'm not grinding them to zero edge. I'm leaving them at about 0.015-0.020", per Brad at Peter's Heat Treat. He said that should keep them straight during the quench. I know that's not a super thin edge, but it's good enough for me. I'm not making these for knife nuts. That behind-the-edge thickness will be durable and still perform well. I can always grind them thinner after if I want, but I likely won't.

Thanks for all the replies, guys. You have confirmed what I suspected. I'm going to take them up to a finer grit before sending them out. I will likely go to 220 or 320 grit. Maybe 400. We will see.
Click to expand...

These are your FIRST knives?! Yup I'm gonna sell everything cause I'm doing something wrong! Great work
 
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